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Mike
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Discussion Starter #1
What is the best approach for welding a Comp Engineering sump to a stock tank. Notch the sump rails, or attack the tank. I'm figuring there must be a straight forward procedure. Thanks for any help.
 

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TEAM CARB
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I cut the tank a little smaller than sump on sides...and leave more material in the rear (to act as a "baffle")
 

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What do you mean by "attack the tank"??
Just cut out a square slightly smaller than the size of the sump flanges, clean the metal real good and weld the sump over the hole.
 

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Mike
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Discussion Starter #4
This is going to be my first tank, the directions that came with the sump want 2" holes drilled and the sump over that. I just need to be sure that I don't suck air for the fuel injection.
 

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Ass, Gas or Grass
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This is going to be my first tank, the directions that came with the sump want 2" holes drilled and the sump over that. I just need to be sure that I don't suck air for the fuel injection.
Yep, the way Ive always done it is by using holes in a grid pattern and try to put them forward of the sump as possible. Leave a good inch or two at the back of tbe sump solid instead of holes, it makes a baffle effect during the launch so fuel doesnt try to "climb" out of tne back of the sump. When you use 4 or 5 small holes instead of 1 huge rectangle style hole acts like a baffle also.

I like to take the sending unit out and rinse the tank a few times with Dawn dish soap and HOT water, then stick a shopvac hose through the sending unit hole and then cut the holes while holdin the vac hose inside close to where the cutter will come through. After the holes are knocked out, purge the tank with C02 while welding the sump, or find a way to fill the tank FULL of water with the sending unit, filler and vent holes closed up.


Oops, sorry for writing a book on the subject, good luck and show us some pics of the aftermath, err I mean project when its done...:p

Shane...
 

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I ALWAYS take mine to a radiator shop and have them soke it in that hot bath before welding..You can get hurt!!
 

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some of the sumps are a little bigger than others, forget which i use, but i drill 2-3 large holes-on a Chevelle, i slit the side of the sump, kind of bend it to form to the tank, rather than push it towards the rear where the tank turns up
another option is to use the McRobb 1/2" (#8) in/out sending unit, add a tail on the tube to push it further back for launches, instead of welding on a used tank
If you need the #10, then sumping is the way to go
i have miged them, but a tig looks cleaner-and be careful air testing it, a little air will make it look preg., bend it out of shape
 

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Yes you can mig it. I just fill the tank with water and drain before I weld to get the fumes out. It's not big of deal to weld the sump. And yes drill holes don't cut it out
 

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Capri For Sale
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The easiest way to weld a tank is to light it first. Make sure it's empty and that there are 2 open holes in the tank like the fill spout and where the sender goes. Take a torch and light one and it'll burn through to the other. Once it has done this and all the gas is gone it will be filled with an inert gas that's from the root of the tank and won't burn again until it gets refueled again with gas. This method of prepping a tank for welding comes from a mechanic that taught me it in the early seventies. I've been doing it this way since then, never had a problem. It's a lot less messier then a lot of other ways to do it. Sometimes you can get a pretty cool jet engine effect.
 

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T5 & T56 building fool
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<----- mig welded mine and then applied a layer of black rtv over the weld to ensure it does not leak. I used a 1" hole saw and punched 5 holes in it. I can run my car well below 1/4 tank around corners and under hard acceleration without any issues at all.
 

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If it is a new tank make sure you get the oil cleaned off of it and out of it, if not when you weld it it will draw the oil to the weld and cause pinholes and sometimes cracks in the weld.......
 

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<----- mig welded mine and then applied a layer of black rtv over the weld to ensure it does not leak. I used a 1" hole saw and punched 5 holes in it. I can run my car well below 1/4 tank around corners and under hard acceleration without any issues at all.
i have found that gas will eat right through rtv. make sure its welded correctly and pass on the rtv.

put the sump where you want it, then scribe the edge with a punch or a sharpie marker. now you know youre limits. measure flange on sump and cut from there. measure 12 times, cut once.
 

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a good way to get all of the fumes out is to obviously drain it, remove the sender. then take a hose (a shop vac one works), hook one end to the fill neck and the other to a vehicles exhaust pipe and run it for a while. the inert exhaust fumes will force out the gas vapor and then you are clear to weld. i did test mine first with a flame and it was fine.
 

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Back to the front!
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a good way to get all of the fumes out is to obviously drain it, remove the sender. then take a hose (a shop vac one works), hook one end to the fill neck and the other to a vehicles exhaust pipe and run it for a while. the inert exhaust fumes will force out the gas vapor and then you are clear to weld. i did test mine first with a flame and it was fine.
this is what I have been told to do as well
 
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